Vitreous fluorophotometry will be performed in patients with diabetes mellitus without retinopathy, patients with diabetes mellitus with nonproliferative retinopathy, and normal volunteer subjects, age-, number-, and sex-matched to the patients. The amount of fluorescein leakage into the vitreous of patients will be compared to that of the normal subjects. Correlations with other features of diabetes, such as the quality of diabetic control, the existence of subclinical neuropathy and nephropathy, and others will be sought.